Our Atmosphere: How it Makes Life and Weather Possible

Earth's blue atmosphere
View of Earth's cloudscape and stratosphere from 30,000 ft up. Aleksandar Vrzalski/E+/Getty

While most of us refer to the atmosphere by it's nickname, "air", or "the sky," we're not nearly as acquainted with it as we should be. Without the atmosphere, our planet would be lifeless and there would be no weather! Get to know it better with the below facts and figures.

A thin envelope of life

Gazing up into the sky from Earth's surface may give you the impression that the atmosphere goes on infinitely.

But although the sky looks vast, it is very thin compared to the size of the Earth. So thin in fact, if the Earth was the size of a globe, the atmosphere would be the thickness of a piece of paper laid over it! (Of course, since the bulk of the atmosphere is distributed across the troposphere, stratosphere, and mesosphere, the paper wouldn't be of uniform thickness.)

How high does the atmosphere go up?

The atmosphere lies between Earth's surface and outer space. While there isn't a definitive line that marks where the atmosphere stops and outer space begins (the atmosphere thins at higher and higher altitudes and gradually ceases to exist), scientists generally consider the atmosphere to extend from Earth's surface up to an altitude of 62 miles (100 km). To put this into perspective, that's about one fourth the distance New York state is wide.

Our planet Earth is surrounded by a thin layer of gases held in place by gravity.

Without the atmosphere, there would be no life on Earth. Neither would there be such a thing as weather. Why? Well for one, the atmosphere is made up of a collection of gases (commonly known as air) which is suitable for breathing. It also protects all life on Earth by absorbing dangerous UV radiation emitted by the sun, and by storing enough heat (greenhouse effect) to keep the surface warm enough for us to comfortably live on.

 Because it is also the place where the energy exchange between the sun (space) and Earth's surface happens, it produces the processes that we call weather.

A Collection of Gases

The three main gases that make up the atmosphere, or air, are Nitrogen, Oxygen, and Argon. Very small amounts of other gases are also found in air. The following table shows just how much of each gas air contains.

The Chemical Composition of Dry Air
Gas% (by volume)
Nitrogen 78.08
Carbon Dioxide0.0397

Another gas also present in the air at all times is water vapor. The amount of water vapor the air holds (called humidity) varies from location to location, and can change from one hour to the next.    

The atmosphere is described by:

  • Temperature: Air temperature is a measure of the thermal energy of air's gas molecules. The primary supplier of this energy is the sun. The of how the atmosphere heats and cools within a 24-hour period is known as its diurnal cycle.
  • Pressure: Air molecules produce pressure through both their weight and movement. Air pressure (high and low) is one of the basic properties that influences weather.
  • Density: Air density is a measure of air's heaviness, or how closely "packed" air is. Dry air has a density of 1.225 kg/m3.
  • Humidity: Humidity deals with the amount of moisture in the air. 

Our atmosphere is divided into 5 main layers:

  • the troposphere (the lowest layer, where weather happens)
  • stratosphere (home of the ozone layer) 
  • mesosphere (the layer mid-way between Earth's surface and space)
  • thermosphere (the atmosphere's second-highest layer, where the auroras happen)
  • exosphere (the outer-most layer, where weather satellites orbit)

What's the "Blue Halo"?

Earth's atmosphere may be made up of invisible gases, but it doesn't always appear invisible to the naked eye. While individual pockets of air do, in fact, look clear to us up close, when viewed from space, the atmosphere actually appears as a thin, blue halo surrounding the entire planet. This is a result of its gases scattering blue wavelengths of light more than other color wavelengths.

(This rationale is also why the sky appears blue overhead!) 

Now that you're acquainted with the atmosphere, you're one step closer to learning about the types of weather that occur in it! 

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Your Citation
Means, Tiffany. "Our Atmosphere: How it Makes Life and Weather Possible." ThoughtCo, Nov. 2, 2015, thoughtco.com/how-atmosphere-makes-life-weather-possible-3443649. Means, Tiffany. (2015, November 2). Our Atmosphere: How it Makes Life and Weather Possible. Retrieved from https://www.thoughtco.com/how-atmosphere-makes-life-weather-possible-3443649 Means, Tiffany. "Our Atmosphere: How it Makes Life and Weather Possible." ThoughtCo. https://www.thoughtco.com/how-atmosphere-makes-life-weather-possible-3443649 (accessed November 22, 2017).